config: remove no-headers as it may leads to a dead peer not removing

eth/downloader/skeleton.go

@@ -74,6 +74,9 @@ var errTerminated = errors.New("terminated")
 // with a new header, but it does not link up to the existing sync.
 var errReorgDenied = errors.New("non-forced head reorg denied")
 
+// maxBlockNumGapTolerance is the max gap tolerance by peer
+var maxBlockNumGapTolerance = uint64(30)
+
 func init() {
 	// Tuning parameters is nice, but the scratch space must be assignable in
 	// full to peers. It's a useless cornercase to support a dangling half-group.
@@ -793,7 +796,11 @@ func (s *skeleton) executeTask(peer *peerConnection, req *headerRequest) {
 		case headers[0].Number.Uint64() != req.head:
 			// Header batch anchored at non-requested number
 			peer.log.Debug("Invalid header response head", "have", headers[0].Number, "want", req.head)
-			res.Done <- etherror.ErrInvalidHeaderBatchAnchor
+			if req.head-headers[0].Number.Uint64() < maxBlockNumGapTolerance {
+				res.Done <- etherror.ErrHeaderBatchAnchorLow
+			} else {
+				res.Done <- etherror.ErrInvalidHeaderBatchAnchor
+			}
 			s.scheduleRevertRequest(req)
 
 		case req.head >= requestHeaders && len(headers) != requestHeaders:

eth/etherror/errors.go

@@ -8,4 +8,5 @@ var (
 	ErrNotEnoughNonGenesisHeaders = errors.New("not enough non-genesis headers delivered")
 	ErrNotEnoughGenesisHeaders    = errors.New("not enough genesis headers delivered")
 	ErrInvalidHashProgression     = errors.New("invalid hash progression")
+	ErrHeaderBatchAnchorLow       = errors.New("header batch anchor is lower than requested")
 )

eth/protocols/eth/handler.go

@@ -157,12 +157,16 @@ func Handle(backend Backend, peer *Peer) error {
 	for {
 		err := handleMessage(backend, peer)
 		switch {
-		case errors.Is(err, etherror.ErrInvalidHeaderBatchAnchor):
-			// ignore invalid header anchor
-			peer.Log().Warn("Message handling failed with invalid batch request anchor")
-		case errors.Is(err, etherror.ErrNoHeadersDelivered):
-			// ignore no headers delivered
-			peer.Log().Warn("Message handling failed with no headers")
+		// TODO: currently no headers not ignored as it may leads to a dead peer not removing as expected
+		/*
+			case errors.Is(err, etherror.ErrNoHeadersDelivered):
+				// ignore no headers delivered
+				peer.Log().Warn("Message handling failed with no headers")
+		*/
+		case errors.Is(err, etherror.ErrHeaderBatchAnchorLow):
+			// ignore lower header anchor within tolerance
+			peer.Log().Warn("Message handling failed with lower batch anchor")
+
 		case err != nil:
 			peer.Log().Debug("Message handling failed in `eth`", "err", err)
 			return err